The effect of proteolytic enzymes (trypsin, subtilisin, papain) on the activity of pure rabbit pulmonary angiotensin-coverting enzyme will be examined as well as the peptide fragments generated by these treatments. Attempts will be made to isolate certain of these peptides or certain of those produced by the action of cyanogen bromide on the pure converting enzyme. Antibodies directed against the purified peptides will be isolate from antioholoenzyme antibodies. Passive immunization with goat antidog converting enzyme antibody will be examined as an immunologic approach for preventing the development of canine renin-dependent hypetension.